US3003953A - Two-stage process for hydrodenitro-genization of naphtha - Google Patents

Description

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F.G REFORM ERG/A5 IN V EN TOR.

AGENT L. P. EVANS Filed May 28, 1959 O E T I. P T ma is of AY N 5 65A NMA MT 0 .T A N C P c m G l n m h .J. WA B 8 w 5 6 2/ v m 9 dmflhzdlrm Z0 Oct. 10, 1961 TWO-STAGE PROCESS FOR HYDRODENITROGENIZATION OF NAPHTHA TO CONTAMlNANT RECDVEQY AND OR, REF'lNER-f FUEL. MAN? la/ J\ United States Patent 3,003,053 TWO-STAGE PROCESS FOR HYDRODENITRO- GENIZATION OF NAPHTHA Louis P. Evans, Woodbury, N.J., assignor to Socony Mobil Oil Company, Inc., a corporation of New York Filed May 28, 1959, Ser. No. 816,412 7 Claims. (Cl. 208-254) The present invention relates to the pretreatment of hydrocarbon mixtures to remove sulfur and/or nitrogen and, more particularly, to the treatment of petroleum oil fractions to remove nitrogen.

It has been known for several years that it was advantageous to remove sulfur and/or nitrogen from mixtures of hydrocarbons containing organic compounds containing sulfur and/or nitrogen prior to contacting the hydrocarbon mixture with a catalyst subject to at least partial deactivation by either sulfur or nitrogen compounds. It has been found advantageous to remove sulfur from mixtures of hydrocarbons for the purpose of reducing corrosion in subsequent operations. Thus, in 1929 British Patent No. 315,439 issued in which the patentees described the treatment of hydrocarbons in the presence of metallic sulfide at temperatures within the range of 392 to 572 F. The so-treated hydrocarbons, it was disclosed, can be readily employed in other catalytic processes, such as catalytic hydrogenation, and poisoning of the catalyst avoided.

In 1935 British Patent No. 424,531 issued in which the p'atentees disclosed that Frequently in the produc tion of valuable liquid hydrocarbons, in particular knockproof motor fuels and valuable lubricating oils by refining, destructive or aromatizing hydrogenation under pressure at temperatures of 572 to 1022 F., injurious deposits are formed which apparently result from a content of highly unsaturated hydrocarbons, in particular diolefins, or of resins or asphalts in said initial materials.

The patentees recommend that the mixture be hydrogenated under conditions such that only the unsaturatedconstituents are hydrogenated and that the pretreated product be subjected to refining, including a process in which sulfur containing impurities are decomposed and removed, destructive or aromatizing hydrogenation or cracking at a higher temperature than that employed in the pretreatment. 'As catalysts for the hydrogenation these patentees recommend metal compounds of the second to the eighth groups of the periodic system, for example, oxides, phosphides, nitrides, in particular sulfides for example of molybdenum, tungsten, chromium, vanadium, manganese, cobalt, nickel, iron, zinc, rhenium, uranium, tin or mixtures of these and the like.

When the industry reformed only straight run naphthas the sulfur and nitrogen content thereof presented no problem. That is to say it is a relatively simple operation to reduce the sulfur content of straight run naphtha to twenty parts per million (20 p.p.m.) and to simultaneously reduce the nitrogen content to less than one part per million 1 p.p.m.). However, the reduction of sulfur and nitrogen to acceptable levels for reforming over aplatinum-catalyst when pretreating a mixture of hydrocarbons such as coker gasoline containing for example 1 percent of sulfur and 400 p.p.m. of nitrogen presents a more diffcult problem.

For example, a mixture of hydrocarbons containing 650 p.p.m. of sulfur and not more than about 10 p.p.m. of nitrogen can be treated under the conditions set forth in Table I to produce 21 treated mixture of hydrocarbons containing 20 p.p.m. of sulfur and not more than 1 p.p.m. of nitrogen.

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TABLE I Catalyst:

3.3% by weight C00. 16.1% by weight M00 on alumina.

S.c.f./b. is standard cubic feet per barrel.

Under the same conditions employing the same catalyst the nitrogen content of a mixture of hydrocarbons containing 15 p.p.m. of nitrogen cannot be reduced to one p.p.m. However, by reducing the space velocity and/or by increasing the pressure, the rate of circulation of hydrogen, and/or the temperature, the nitrogen content of a mixture of hydrocarbons containing 15 p.p.m. of nitrogen can be reduced to not more than one p.p.m. On the other hand, many units now used for the pretreatment of naphthas to be reformed over platinum catalyst were designed for the relatively low pressure of say 500 p.s.i.g. and the relatively high space velocities and relatively low rates of hydrogen circulation which have been found to give satisfactory reductions in the sulfur and nitrogen contents of straight run naphtha. Consequently, the industry must either build additional equipment for the special treatment of high-nitrogen stocks or operate at reduced space velocities and reduced throughput.

Another solution of the problem is to use platinum catalyst for the removal of nitrogen. Platinum is an excellent catalyst for the removal of nitrogen. Thus, for example, the nitrogen content of a mixture of hydrocarbons containing 15 p.p.m. of nitrogen can be reduced to 0.2 p.p.m. by contact with platinum catalyst under the same conditions as set forth in Table I. However, such a platinum catalyst costs about five to fourteen times the cost of a satisfactory cobalt-molybdenum catalyst.

It has now been discovered that, while under the relatively mild conditions given in Table III a cobalt-molybdenum catalyst will reduce the nitrogen content of a mixture of hydrocarbons from 15 p.p.m. to 1.6 p.p.m. and a platinum catalyst under the same conditions will reduce the nitrogen content of a mixture of hydrocarbons from 15 p.p.m. to 0.2 p.p.m., the nitrogen content of a mixture of hydrocarbons can be reduced from 15 p.p.m. to 0.5 p.p.m. by contacting the mixture of hydrocarbons first with a cobalt-molybdenum catalyst and then with a platinum catalyst under'the conditions set forth in Table II.

7 TABLE II Tons of catalyst/ 10,000 b ll Pressure, psi g 400 to 500 Temperature, "F 650 to 800 Space velocity, v./hr./v 2 to 5 Circulation rate of hydrogen, s.c.f./b 500 to 1000 It is another object of the present invention to provide a method of hydrodecontarninating a mixture of hydrocarbons containing organic compounds of nitrogen comprising first contacting said mixture with a catalyst comprising a mixture of oxides and/or sulfides of cobalt and molybdenum and then with a catalyst comprising platinum-group metal on alumina wherein the volume of the catalyst comprising oxides and/or sulfides of cobalt and molybdenum is at least equal to, and not more than about ten times, the volume of the catalyst comprising platinum-group metal on alumina. It is a further object of the present invention to provide a method of hydrodecontaminating a mixture of hydrocarbons containing organic compounds of nitrogen which comprises contacting said mixture first with a catalyst comprising a mixture of oxides and/ or sulfides of cobalt and molybdenum and then with a catalyst comprising platinum-group metal on alumina wherein the oil to be hydrodecontaminated is contacted with a total amount of both catalysts at a rate not exceeding about 10 to 30 tons per 10,000 barrels of said mixture per day i.e., at an overall liquid hourly space velocity in the range of about 5.5 to about 1.83, and wherein the volume of the catalyst comprising oxides and/ or sulfides of cobalt and molybdenum is about one to about three times the volume of said catalyst comprising platinum-group metal on alumina. It is also within the scope of the present inven tion to provide a method of hydrodecontaminating a mixture of hydrocarbons containing organic nitrogen compounds which comprises contacting said mixture first with a non-noble metal catalyst having hydrogenating, hydrodesulfurizing and hydrodenitrogem'zing capabilities and then with a catalyst comprising a metal of the platinum group of the eighth group of the periodic table on alumina wherein the oil to be hydrodecontaminated is contacted with a total quantity of both catalysts at the rate of about 10 to about 30 tons per 10,000 barrels of said hydrocarbon mixture per day i.e., at an overall liquid hourly space velocity in the range of about 5.5 to about 1.83, and wherein the volume of said non-noble metal catalyst is at least equal to, and not more than ten times, the volume of said platinum group catalyst. Other objects and advantages will become apparent to those skilled in the art from the following description taken in conjunction with the drawing in which FIGURE 1 is a flow sheet showing the flow of liquid and gases employing a single reactor and two static beds of catalyst.

At the outset it must be emphasized that passage of a mixture of hydrocarbons containing organic nitrogen compounds successively through two beds of catalyst as described hereinafter results in a reduction in the nitrogen content of the mixture of hydrocarbons which is more than just the additive effect of the two beds of catalyst. This is manifest from an inspection of the data presented in Table III.

TABLE HI Feed (boiling range100 F. to 400 F.)

Nitrogen, pp in 15 Sulfur, p.p m 650 Olefins, vol. percent 4 Conditions:

Tons of catalyst per 10,000 h./d 11 Pressure, p si 5: 425 Temperature, F 690 Liquid hourly space velocity, v./hr./v Rate of circulation of hydrogen, s.c.f./b 500 Case I Case II Case III avolumes Catalyst A B A+1 volume B Hydrodecontaminated Product:

Nitrogen, p.p.m 1. 6 0. 2 0. 5 Nitrogen removed, p.p.m 13.4 14. 8 l4. 5 Sulfur, ppm 20 20 20 Sulfur removed, percent 97 97 97 Catalyst A3.3 weight percent 000; 16.1 weight percent M00 on the cobalt-molybdenum catalyst alone less 25% of the nitrogen removed by the platinum catalyst alone. That is 15 p.p.m. (feed) minus 75% of 13.4 p.p.m. less 25% of 14.8 ppm. is 1.25, and greater than 0.5 ppm. Therefore, it is apparent that the two catalysts when used as described hereinafter work together to produce a result that is not merely the additive effect of each.

In accordance with the principles of the present invention a mixture of hydrocarbons generally containing not more than about 20 p.p.m. of nitrogen is contacted successively with a non-noble metal catalyst, preferably sup ported on alumina, having hydrogenating, hydrodesulfurizing and hydrodenitrogenizing capabilities, and with a platinum-group metal catalyst, preferably supported on alumina. Illustrative of the non-noble metal catalyst are the various cobalt-molybdenum catalysts comprising about 0.8 to about 3.0 percent by weight of cobalt and about 2.0 to about 16.5 percent by weight of molybdenum as oxides and/or sulfides and the balance alumina. Illustrative of the platinum group catalysts are catalysts comprising about 0.01 to about 2.0 percent (preferably 0.3 to 0.6) by weight platinum, up to about 2.0 percent by weight of chlorine and/ or fluorine supported on alumina. The mixture of hydrocarbons to be hydrodecontaminated is contacted with about 10 to about 30 tons of catalyst per 10,000 barrels of mixture of hydrocarbons per day of which about 50 to about percent is the non-noble metal catalyst and about 10 to about 50 percent, preferably about 20 to 30 percent, is platinum group catalyst. Reaction conditions for hydrodecontaminating a mixture of hydrocarbons containing not in excess of 20 ppm. of nitrogen to produce a decontaminated product containing not more than 1 ppm. of nitrogen are given in Tables IV and V wherein the non-noble metal catalyst is fifty percent by volume of the total volume of catalyst charged to both reaction zones.

TABLE IV First reaction zone Catalyst:

3.3 wt. percent C00 16.1 wt. percent M00 Balance alumina Broad Preferred Pressure, p.s.i.g 400 to 800 400 to 500 Temperature, F 500 to 800 650 to 800 Space Velocity, v./hr./v 2 to 8 2 to 5 Circulation Rate of Hydrogen, s.c.f.,lb 300 to 3,000 500 to 1,000

TABLE V Second reaction zone Catalyst 0.6 wt. percent Pt 0.6 wt. percent halogen Balance alumina Broad Preferred Pressure, p.s.i.g 400 to 800 400 to 500 Temperature, F 500 to 800 650 to 800 Space Velocity, v./hr./v 2 t0 8 2 to 5 Circulation Rate of Hydrogen, s.c.f./b. 300 to 3, 000 500 to 1, 000

In the drawing is illustrated a typical flow diagram of a means employing a static bed of non-noble metal catalyst superposed on a static bed of platinum-group metal catalyst for reducing the nitrogen content of a hydrocarbon mixture for use as a feed to a reaction employing a nitrogen sensitive catalyst, i.e., a catalyst which is re versibly or irreversibly poisoned by nitrogen compounds. (A reversible poisoning is one in which the activity of the catalyst can be restored. An ireversible poisoning is one in which the activity of the catalyst cannot be restored by known means.) Typical of a catalyst which is poisoned by contact with nitrogen compounds are the platinum reforming catalysts presently used. It has been found that platinum reforming catalysts lose activity at an intolerable rate when reforming mixtures of hydrocarbons, such as naphtha, containing more than 1 p.p.m. of nitrogen. Accordingly, a naphtha to be reformed on Contact with a platinum reforming catalyst must have a nitrogen content not in excess of 1 p.p.m. if the onstream time of the reforming catalyst is to be of practical duration. Furthermore, it is manifest that, even though the present method of hydrodenitrogenizing a feed to a reaction in which a nitrogen-sensitive catalyst is used is at least 95 percent efiicient, i.e., removes at least 95 percent of the nitrogen, there is a maximum concentration at which the present method will produce a feed having the required nitrogen content of not more than a given p.p.m. Consequently, the nitrogen content of the feed to a hydrodenitrogenizing process such as described herein cannot exceed about 20 p.p.m. when a pretreated prodnot containing not more than 1 p.p.m. of nitrogen must be produced. However, when the nitrogen-sensitive catalyst used in a subsequent operation has a nitrogen tolerance greater than 1 p.p.m. the feed to the pretreating operation can be proportionately higher. Accordingly, the feed to the pretreater must contain not more than B -C p.p.m. of mtrogen where Nitrogen Removed O.a- 1 100 B=maximum p.p.m. nitrogen tolerated in pretreater product =maximum p.p.m. of nitrogen in feed to pretreater Since generally about 95 to about 96 percent of the nitrogen in a naphtha feed is removed by the method of the present invention it is manifest that the feed to the pretreater disclosed in the present invention must not exceed about 20 to about 25 p.p.m. in order to produce a feed for a subsequent catalytic reaction containing not more than 1 p.p.m. of nitrogen.

Nevertheless, mixtures of hydrocarbons containing more than of nitrogen can be treated provided a mixture of hydrocarbons is available as a diluent. The diluent can be a material which is inert in the subsequent catalytic reaction and later removed as by distillation or a material which is to be subjected to the same subsequent catalytic reaction in conjunction with the mixture having the excessive nitrogen content. Thus, for example, an undiluted coker naphtha containing 140 p.p.m. of nitrogen cannot be treated under the conditions set forth hereinafter to provide a reformer feed containing 1 p.p.m. of nitrogen. On the other hand, in most refineries the volume of straight run naphtha to be reformed is usually 'a multiple of the volume of coker naphtha to be reformed. Consequently, the straight run naphtha can be used as a diluent. Thus, a coker naphtha containing the concentration of nitrogen shown in Table VI can be diluted with a straight run naphtha in the ratio of to 95 volumes of straight run naphtha to 95 to 5 volumes of coker naphtha to provide a pretreater feed containing not more than of nitrogen from which a reformer feed containing not more than 1 p.p.m. of nitrogen can be produced.

TABLE VI Ooker Naphtha Straight Run N aphtha Pretreater Percent Product or Feed N0. Nitrogen Reformer p.p.m. Parts p.p.m. Parts Removed Feed.

of Niby Volof Niby Volp.p.m. trogen ume trogen ume Nitrogen To illustrate the method of the present invention reference is made to the treatment of a mixture of coker naphtha containing p.p.m. of nitrogen and a straight 11in naphtha containing 1 p.p.m. of nitrogen in proportions to provide a mixture containing about 20 p.p.m. of nitrogen.

A mixture of coker and straight run naphtha containing about 20 p.p.m. of nitrogen is drawn from a source not shown through pipe 1 by pump 2 and discharged into pipe 3 at a pressure greater than that in reactor 11. The naphtha mixture or pretreater feed flows through pipe 3 to heat exchanger 4 where the pretreater feed is in indirect heat exchange relation with the effluent of reactor 11. From heat exchanger 4 the pretreater feed flows through pipe 5 to heat exchanger 6 where the pretreater feed is in indirect heat exchange relation with the effluent of reactor 11 flowing thereto through conduit 14 from reactor 11. From heat exchanger '6 the pretreater feed flows through pipe 7 to coil 8 in heater 9.

In heater 9 the pretreater feed is heated to reaction temperature within the limits of about 500 toabout 800 F., preferably about 650 to about 800 F. The heated pretreater feed'fiows from heater 9 through conduit 10 to reactor 11. At some point in conduit 10 intermediate to heater 9 and to reactor 11 hydrogen or hydrogen-containing gas such as hydrogen-containing gas flowing from a reformer (not shown) through conduit 35 is mixed with the heated pretreater feed in the proportion of about 500 to about 1000 standard cubic feet of hydrogen per barrel of pretreater feed. As indicated the hydro gen-containing gas can be supplemented with gas from other sources introduced into conduit 3-5 through conduit 32.

The mixture of pretreater feed and hydrogen, now designated charge mixture, flows downwardly in contact with a static bed of non-noble metal catalyst, e.g., a mixture of oxides of cobalt and molybdenum on an alumina support through the first reaction zone 12. The efliuent of first reaction zone 12 comprising feed naphtha, hydrogen derivatives of sulfur and nitrogen, i.e., hydrogen sulfide and ammonia, unhydrogenated organic sulfur and nitrogen compounds and hydrogen enters the second reaction zone 13 wherein the first reaction zone efiluent contacts a static bed of platinum-group metal catalyst, e.-g., platinum on alumina. The first reaction zone efiiuent flows downwardly through second reaction zone 13 to the outlet thereof. (Those skilled in the art will recognize that reaction zones 12 and 13 can bein separate reactors.)

From reaction zone 13 the effluent therefrom flows through conduit 14 to heat exchanger 6 Where the chinent from reaction zone 13, designated final effluent, is in indirect heat exchange relation with the pretreater feed as described hereinbefore, From heat exchanger 6 the final efliuent flows through conduit 15 to heat exchanger 16 where the final effiuent is in indirect heat exchange sure the lowest boiling hydrocarbon to be further catalytically treated is condensed. For reformer feed, the temperature of the final eiiiuent is reduced to a temperature at which C and heavier hydrocarbons are liquid at the existing pressure. From cooler 19 the condensed and uncondensed final efiiuent flow through conduit 20 to liquid-gas separaotr 21.

In liquid-gas separator 21 the uncondensed final efiiuent, in the illustrative case the C and lighter hydrocarbons, hydrogen, and volatile hydrogen derivatives of contaminants, sulfur and nitrogen insoluble in the condensed final eflluent at the temperature and pressure existing in liquid gas separator 21, separates from the condensed final efiiuent and fiows through conduit 22 to conduit 36 and thence to the refinery fuel main and/or recovery of the sulfur and ammonia by known means. The condensed final effluent, hereinafter designated condensate, flows through pipe 23 to the suction side of pump 24. Pump 24 discharges the condensate into pipe 25 through which the condensate flows to heat exchanger 26. In heat exchanger 26, the condensate is in indirect heat exchange relation with the bottoms of stripper 29 flowing therefrom through pipe 39. From heat exchanger 26 the condensate flows through pipe 27 to heat exchanger 16 where the condensate is in indirect heat exchange relation with the reactor effluent fiowing from heat exchang er 6 through conduit 15 as described previously. From heat exchanger 16 the condensate flow through pipe 28 to stripper 29. Stripping gas such as hydrogen-containing gas flowing from a reformer (not shown) through conduit 37 under control of valve 38 is introduced into stripper 29 in any suitable manner to provide intimate contact between the stripping gas and the condensate under conditions of temperature and pressure to remove substantially all of the volatile hydrogen derivatives of the contaminants.

The stripping gas, in this instance hydrogen-containing gas, flows from stripper 29 through conduit 30 to compressor 31 and thence through conduits 32 and to conduit 10 where it is mixed with the pretreater feed in the proportions disclosed hereinbefore to make the charge mixture. When the supply of hydrogen-containing gas is sufiicient to meet the demands for the hydrogenation of the pretreater feed and for stripping the condensate without cycling the strippers overhead to reactor 11, the stripper overhead flows through conduit 33 under control of valve 34 to conduit 36 where it is mixed with the gas from separator 21.

The stripped condensate containing not more than innocuous concentrations of catalyst poisons in the illustrative case not more than 1 ppm. of nitrogen, flows from stripper 23 through pipe 39 to heat exchanger 26 where the stripped condensate, i.e., stripper bottoms, is in indirect heat exchange relation with the condensate flowing from separator 21 through pipe 25 as described hereinbefore. The stripper bottoms flows from heat exchanger 26 through pipe 40 to the charge pump of the subsequent operation (reforming in the illustrative case) or to storage.

From the foregoing description of the method of the present invention for hydrodecontaminating a mixture of hydrocarbons to be contacted with a catalyst sensitive to a contaminant in said mixture of hydrocarbons which contaminant reacts with hydrogen in the presence fo a hydrogenating catalyst to form volatile hydrogen derivatives of said contaminants those skilled in the art will understand that the method of the present invention comprises contacting a mixture of hydrocarbons containing a contaminant of the class defined in a concentration not greater than where B is the innocuous concentration in ppm. of the contaminant and On is the percent of said contaminant remaining after the hydrodecontamination in the presence of hydrogen and a non-noble hydrogenation catalyst having hydrodecontaminating capabilities in a first reaction zone, contacting the effluent of said first reaction zone comprising hydrogen and unreacted compounds of said contaminant with a platinum-group metal catalyst, and separating volatile hydrogen derivatives of said contaminant from the treated hydrocarbons of said hydrocarbons mixture to obtain a hydrocarbon mixture as feed for a subsequent reaction in the presence of a contaminant-sensitive catalyst containing not more than innocuous concentration of said contaminant, said non-noble catalyst being used in volume at least about equal to, but not greater than about ten times, the volume of said platinum group catalyst and the total volume of both catalysts being not more than about 30 tons per 10,000 barrels of said hydrocarbon mixture treated per day,

I claim:

1. A method of hydrodenitrogenizing naphtha which comprises charging a first reaction stage with particleform solid non-noble metal hydrogenating catalyst having hydrdenitrogenizing capabilities, charging a second reaction stage with particle-form solid platinum-group metal hydrogenating catalyst having hydrodenitrogenizing capabilities, the total amount of said catalysts charged to said first and second reaction stages being in the proportion of about 10 to about 30 tons per 10,000 barrels of feed per day, the aforesaid non-noble metal catalyst being about 50 to about percent by volume and the aforesaid platinum-group metal catalyst being the balance to make percent by volume of the aforesaid about 10 to about 30 tons, passing feed containing at least 15 ppm. of nitrogen comprising naphtha containing more than 15 ppm. of nitrogen and a diluent successively through said first and second reaction stages to obtain an effluent of which the C and heavier hydrocarbons boiling in the naphtha range contain not more than 1 p.p.m. of nitrogen whilst maintaining a pressure in the range of about 400 to about 800 p.s.i.g., a temperature in the range of about 500 to 800 F., and a hydrogen circulation of about 300 to about 3,000 standard cubic feet of hydrogen per barrel of said feed, in each of said first and second reaction stages maintaining in said first reaction stage a liquid hourly space velocity in the range of about 2 to about 11 and in said second reaction stage a liquid hourly space velocity of about 4 to about 55 dependent upon the liquid hourly space velocity in the said first reaction stage and the volume of catalyst in said second stage, and separating from the aforesaid effluent a C and heavier hydrocarbon fraction boiling in the naphtha range containing not more than 1 p.p.m. of nitrogen.

2. The method set forth in claim 1 wherein the nonnoble metal hydrogenating catalyst is about 70 to about 80 percent by volume of the about 10 to about 30 tons per 10,000 barrels of feed per day.

3. The method set forth in claim 1 wherein the diluent is naphtha containing not more than 1 ppm. of nitrogen.

4. The method set forth in claim 1 wherein the nonnoble metal hydrogenating catalyst is selected from the group consisting of a mixture of oxides of cobalt and molybdenum on alumina support, and a mixture of oxides and sulfides of cobalt and molybdenum on alumina support.

5. The method set forth in claim 4 wherein the platinum-group metal hydrogenating catalyst comprises about 0.3 to about 0.6 percent by weight of platinum and up to about 2 percent by weight of halogen selected from the group consisting of chlorine and fluorine on alumina support.

6. The method set forth in claim 1 wherein the nonnoble metal hydrogenating catalyst comprises about 3.3 percent by weight of oxide of cobalt, about 16.1 percent by weight of oxide of molybdenum and the balance alumina, wherein the platinum-group metal hydrogenat- 9 ing catalyst comprises about 0.6 percent by weight of platinum and about 0.6 percent by weight of chlorine on alumina support, wherein the feed comprises thermally cracked naphtha and straight run naphtha and contains more than 15 but not more than about 31 ppm. of nitrogen, wherein the temperature in both stages is in the range of about 650 to about 800 F., wherein the pressure in both stages is in the range of about 400 to about I 500 p.s.i.g., wherein the liquid hourly space velocity in the first stage is about 2 to about 5, and wherein the hydrogen circulation is about 500 to about 1,000 standard cubic feet of hydrogen per barrel of feed.

7. The method set forth in claim 6 wherein the nonnoble metal hydrogenating catalyst is about 50 percent by volume.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A METHOD OF HYDRODENITROGENIZING NAPHTHA WHICH COMPRISES CHARGING A FIRST REACTION STAGE WITH PARTICLEFORM SOLID NON-NOBLE METAL HYDROGENATING CATALYST HAVING HYDRDENITROGENIZING CAPABILITIES, CHARGING A SECOND REACTION STAGE WITH PARTICLE-FORM SOLID PLATINUM-GROUP METAL HYDROGENATING CATALYST HAVING HYDRODENITROGENIZING CAPABILITIES, THE TOTAL AMOUNT OF SAID CATALYST CHARGED TO SAID FIRST AND SECOND REACTION STAGE BEING IN THE PROPORTION OF ABOUT 10 TO ABOUT 30 TONS PER 10,000 BARREL OF FEED PER DAY, THE AFORESAID NON-NOBLE METAL CATALYST BEING ABOUT 50 TO ABOUT 90 PERCENT BY VOLUME AND THE AFORESAID PLATINUM-GROUP METAL CATALYST BEING THE BALANCE TO MAKE 100 PERCENT BY VOLUME OF THE AFORESAID ABOUT 10 TO ABOUT 30 TONS, PASSING FEED CONTAINING AT LEAST 15 P.P.M. OF NITROGEN COMPRISING NAPHTHA CONTAINING MORE THAN 15 P.P.M. OF NITROGEN AND A DILUENT SUCCESSIVELY THROUGH SAID FIRST AND SECOND REACTION STAGE TO OBTAIN AN EFFLUENT OF WHICH THE C5 AND HEAVER HYDROCARBONS BOILING IN THE NAPHTHA RANGE CONTAIN NOT MORE THAN 1 P.P.M. OF NITROGEN WHILST MAINTAINING A PRESSURE IN THE RANGE OF ABOUT 400 TO ABOUT 800 P.S.I.G., A TEMPERATURE IN THE RANGE OF ABOUT 500* TO 800*F., AND A HYDROGEN CIRCULATION OF ABOUT 300 TO ABOUT 3,000 STANDARD CUBIC FEET OF HYDROGEN PER BARREL OF SAID FEED, IN EACH OF SAID FIRST AND SECOND REACTION STAGES MAINTAINING IN SAID FIRST REACTION STAGE A LIQUID HOURLY SPACE VELOCITY IN THE RANGE OF ABOUT 2 TO ABOUT 11 AND IN SAID SECOND REACTION STAGE A LIQUID HOURLY SPACE VELOCITY OF ABOUT 4 TO ABOUT 55 DEPENDENT UPON THE LIQUID HOURLY SPACE VELOCITY IN THE SAID FIRST REACTION STAGE AND THE VOLUME OF CATALYST IN SAID SECOND STAGE, AND SEPARATING FROM THE AFORESAID EFFLUENT A C5 AND HEAVIER HYDROCARBON FRACTION BOILING IN THE NAPHTHA RANGE CONTAINING NOT MORE THAN 1 P.P.M. OF NITROGEN.

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